# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=500

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**Page:** 501

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## [RFQ: InplaceLinalg](https://discourse.julialang.org/t/rfq-inplacelinalg/23195)

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**Author:** [@davidavdav](https://discourse.julialang.org/u/davidavdav)\
**Replies:** 9\
**Last updated:** [April 18, 2019, 11:49am UTC](https://discourse.julialang.org/t/rfq-inplacelinalg/23195 "2019-04-18T11:49:01Z")

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Hello, We’ve noticed that the broadcasting assignment operator .= does a good job in in-place assignment of the LHS in some cases, but not so in others. I suppose .= is really about broadcasting, and not about in-place…

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## [CUDAnative/CuArrays: performance regression for memcopy code](https://discourse.julialang.org/t/cudanative-cuarrays-performance-regression-for-memcopy-code/23253)

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**Author:** [@samo](https://discourse.julialang.org/u/samo)\
**Replies:** 3\
**Last updated:** [April 18, 2019, 7:58am UTC](https://discourse.julialang.org/t/cudanative-cuarrays-performance-regression-for-memcopy-code/23253 "2019-04-18T07:58:40Z")

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Hi all, I just updated CUDAnative, CUDAdrv, CuArrays and GPUArrays to use the master version. Now, the following test for sustained performance of device to device memory copy shows a performance regression from about 5…

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## [DataFrames: is it possible to group data horizontally (multilevel)?](https://discourse.julialang.org/t/dataframes-is-it-possible-to-group-data-horizontally-multilevel/23239)

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**Author:** [@mike\_k](https://discourse.julialang.org/u/mike_k)\
**Replies:** 10\
**Last updated:** [April 17, 2019, 5:11pm UTC](https://discourse.julialang.org/t/dataframes-is-it-possible-to-group-data-horizontally-multilevel/23239 "2019-04-17T17:11:25Z")

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Dear community, suppose we have a simple dataframe df = DataFrame(Cat1 = \["A", "A", "B", "B"\], Cat2 = \["C", "D", "C", "D"\], val1 = 1:4, val2 = 5:8) which looks like julia\> …

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## [Is it possible to selectively update the params in Flux.jl?](https://discourse.julialang.org/t/is-it-possible-to-selectively-update-the-params-in-flux-jl/23198)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 9\
**Last updated:** [April 17, 2019, 10:54am UTC](https://discourse.julialang.org/t/is-it-possible-to-selectively-update-the-params-in-flux-jl/23198 "2019-04-17T10:54:49Z")

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I can’t seem to update the weights selectively. See below example where x is a set of 3 weights and I want to only update, say the first component. But can’t seem to do so. Is there a way to do that? x = param(rand(3)) …

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## [What's the difference between Null, NA, #NULL, nothing, ""](https://discourse.julialang.org/t/whats-the-difference-between-null-na-null-nothing/6468)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 6\
**Last updated:** [April 17, 2019, 10:25am UTC](https://discourse.julialang.org/t/whats-the-difference-between-null-na-null-nothing/6468 "2019-04-17T10:25:42Z")

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I am a bit lost on the many ways to represent the “empty” concept in Julia… What is the difference between Null (from Nulls.jl), NA (From DataFrames), #NULL from NullableArrays, Nullable container (from base), nothing (…

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## [Robust or global multivariate rootfinder](https://discourse.julialang.org/t/robust-or-global-multivariate-rootfinder/23169)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 8\
**Last updated:** [April 16, 2019, 3:31pm UTC](https://discourse.julialang.org/t/robust-or-global-multivariate-rootfinder/23169 "2019-04-16T15:31:10Z")

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I have a function in about 3–7 variables (varies, ideally 7) and I am looking for a root. It is best to treat the function as a “black box”, just delivering values and not derivatives, though I will try to make it work …

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## [How to use "plotyy" for showing several sets of graphs in one plot](https://discourse.julialang.org/t/how-to-use-plotyy-for-showing-several-sets-of-graphs-in-one-plot/23204)

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**Author:** [@mirtah](https://discourse.julialang.org/u/mirtah)\
**Replies:** 3\
**Last updated:** [April 16, 2019, 2:58pm UTC](https://discourse.julialang.org/t/how-to-use-plotyy-for-showing-several-sets-of-graphs-in-one-plot/23204 "2019-04-16T14:58:02Z")

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Dear all. I would like to know how to use “plotyy” for showing several sets of graphs in one plot. Thank you very much Best regards using PyPlot,SetPyPlot plotyy(A1, B1, C1, D1) plotyy(A2, B2, C2, D2) plotyy(A3, B…

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## [DataFrames: how to calculate conditional mean values in grouped dataframe?](https://discourse.julialang.org/t/dataframes-how-to-calculate-conditional-mean-values-in-grouped-dataframe/23194)

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**Author:** [@mike\_k](https://discourse.julialang.org/u/mike_k)\
**Replies:** 6\
**Last updated:** [April 16, 2019, 2:23pm UTC](https://discourse.julialang.org/t/dataframes-how-to-calculate-conditional-mean-values-in-grouped-dataframe/23194 "2019-04-16T14:23:11Z")

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Dear Community, I have a DataFrame df, which I group for instance like: foo = by(df, \[:param1, :param2\], :res =\> mean) Here, columns param1 and param2 store parameter values and column res stores result values. Foo sh…

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## [StatsPlots - trying to extend boxplot](https://discourse.julialang.org/t/statsplots-trying-to-extend-boxplot/23190)

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**Author:** [@BioTurboNick](https://discourse.julialang.org/u/BioTurboNick)\
**Replies:** 3\
**Last updated:** [April 16, 2019, 2:09pm UTC](https://discourse.julialang.org/t/statsplots-trying-to-extend-boxplot/23190 "2019-04-16T14:09:12Z")

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I’m trying to extend boxplot to show all individual datapoints. However, I can’t seem to get Julia to use the local development files. I’ve cloned StatsPlots locally, opened the folder in Juno, used \]activate . followed…

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## [How to round off a Float32 to Int32 on GPU](https://discourse.julialang.org/t/how-to-round-off-a-float32-to-int32-on-gpu/23129)

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**Author:** [@11116](https://discourse.julialang.org/u/11116)\
**Replies:** 4\
**Last updated:** [April 16, 2019, 11:11am UTC](https://discourse.julialang.org/t/how-to-round-off-a-float32-to-int32-on-gpu/23129 "2019-04-16T11:11:34Z")

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using CUDAdrv, CUDAnative,CuArrays #try to convert a Float32 to Int32 function addKernel!(x,y,θ) x = threadIdx().x+blockDim().x\*(blockIdx().x-1) m = x\*CUDAnative.cos(θ)+CUDAnative.sin(θ)\*y z = Int32(m) x\[…

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## [Turtle graphics TUI or GUI](https://discourse.julialang.org/t/turtle-graphics-tui-or-gui/23177)

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**Author:** [@chakravala](https://discourse.julialang.org/u/chakravala)\
**Replies:** 4\
**Last updated:** [April 16, 2019, 9:08am UTC](https://discourse.julialang.org/t/turtle-graphics-tui-or-gui/23177 "2019-04-16T09:08:16Z")

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What julia packages provide a turtle graphics terminal / graphical user interface for drawing?

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## [Makie object management / scene refresh](https://discourse.julialang.org/t/makie-object-management-scene-refresh/15526)

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**Author:** [@jac299792458](https://discourse.julialang.org/u/jac299792458)\
**Replies:** 7\
**Last updated:** [April 16, 2019, 12:28am UTC](https://discourse.julialang.org/t/makie-object-management-scene-refresh/15526 "2019-04-16T00:28:42Z")

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Hi all (@sdanisch :stuck\_out\_tongue\_winking\_eye: ), I have an existing scene, rendered to the screen, containing a DAG. As the execution of the Julia script progresses, the DAG changes. nodes are added, labels are mov…

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## [Plots: gr(), after savefig() plots become ugly](https://discourse.julialang.org/t/plots-gr-after-savefig-plots-become-ugly/22591)

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**Author:** [@davide](https://discourse.julialang.org/u/davide)\
**Replies:** 4\
**Last updated:** [April 15, 2019, 9:06am UTC](https://discourse.julialang.org/t/plots-gr-after-savefig-plots-become-ugly/22591 "2019-04-15T09:06:16Z")

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Using Plots, when I plot with the gr() backend I get a nice graph (in its own window). The savefig() command closes that window; after that, next plots will be displayed in a new window, but with ugly graphics (and no tr…

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## [I am getting an error when building CuArrays](https://discourse.julialang.org/t/i-am-getting-an-error-when-building-cuarrays/23059)

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**Author:** [@mgalenb](https://discourse.julialang.org/u/mgalenb)\
**Replies:** 7\
**Last updated:** [April 15, 2019, 5:22am UTC](https://discourse.julialang.org/t/i-am-getting-an-error-when-building-cuarrays/23059 "2019-04-15T05:22:54Z")

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I have installed CUDA 9.0 toolkit and Xcode and i have exported to PATH but when i build CuArrays i get this error: Building SpecialFunctions → \`~/.julia/packages/SpecialFunctions/fvheQ/deps/build.log\` Building CUDA…

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## [Current state of the relationship between Plots and Makie](https://discourse.julialang.org/t/current-state-of-the-relationship-between-plots-and-makie/20607)

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**Author:** [@ValdarT](https://discourse.julialang.org/u/ValdarT)\
**Replies:** 4\
**Last updated:** [April 14, 2019, 7:48pm UTC](https://discourse.julialang.org/t/current-state-of-the-relationship-between-plots-and-makie/20607 "2019-04-14T19:48:32Z")

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There was a plan that Makie should eventually replace (or merge with) Plots. I would appreciate if someone in the know would give an update on the current state of affairs regarding this.

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## [Backward pass for sampling](https://discourse.julialang.org/t/backward-pass-for-sampling/23071)

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**Author:** [@Roger-luo](https://discourse.julialang.org/u/Roger-luo)\
**Replies:** 2\
**Last updated:** [April 14, 2019, 5:13pm UTC](https://discourse.julialang.org/t/backward-pass-for-sampling/23071 "2019-04-14T17:13:13Z")

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I’m wondering if people have implement this before somewhere, like Turing? but I’m not very familiar with Turing and how it is integrated with ADs, so maybe someone could point me to reference: Given a parameterized dis…

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## [Parallel for breaks in SDL application](https://discourse.julialang.org/t/parallel-for-breaks-in-sdl-application/22937)

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**Author:** [@xor0110](https://discourse.julialang.org/u/xor0110)\
**Replies:** 4\
**Last updated:** [April 14, 2019, 12:50pm UTC](https://discourse.julialang.org/t/parallel-for-breaks-in-sdl-application/22937 "2019-04-14T12:50:21Z")

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I am doing my first attempt ever at Julia with multi-threading. I wrote a program to draw a fractal using SDL and SIMD instructions. That works well. To render each frame I just do a loop over all pixels, calculate a val…

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## [How to change the background color in GR?](https://discourse.julialang.org/t/how-to-change-the-background-color-in-gr/22776)

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**Author:** [@jarmstrong](https://discourse.julialang.org/u/jarmstrong)\
**Replies:** 2\
**Last updated:** [April 13, 2019, 4:22pm UTC](https://discourse.julialang.org/t/how-to-change-the-background-color-in-gr/22776 "2019-04-13T16:22:19Z")

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I use GR as a quick plotting back-end, as it’s faster than loading the Plots package. Can anyone tell me how to change the default background color of GR plots from transparent to white? (Ideally permanently). I usually…

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## [Select and rename columns in IndexedTables.jl / JuliaDB.jl](https://discourse.julialang.org/t/select-and-rename-columns-in-indexedtables-jl-juliadb-jl/23077)

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**Author:** [@qsong](https://discourse.julialang.org/u/qsong)\
**Replies:** 0\
**Last updated:** [April 12, 2019, 1:22pm UTC](https://discourse.julialang.org/t/select-and-rename-columns-in-indexedtables-jl-juliadb-jl/23077 "2019-04-12T13:22:24Z")

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With dplyr experience, I am just learning and testing IndexedTables.jl / JuliaDB.jl. The following seems verbose. (using https://github.com/oxinabox/Pipe.jl) julia\> a = table(\[1,1,1,2,2,2\], \[1,1,2,2,1,1\], \[1,4,2,5,6,7\],…

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## [Lora Package](https://discourse.julialang.org/t/lora-package/23072)

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**Author:** [@marouane](https://discourse.julialang.org/u/marouane)\
**Replies:** 7\
**Last updated:** [April 13, 2019, 8:31am UTC](https://discourse.julialang.org/t/lora-package/23072 "2019-04-13T08:31:57Z")

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Hello, i decided to download Julia 1.1.0 and leave the 0.7 version and i wanted to add the Lora package but i couldn’t because it was restricted by julia compatibility requirements to versions, so i wanna know what is t…

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## [JuMP: use AD within a JuMP model to define a derivative-based constraint](https://discourse.julialang.org/t/jump-use-ad-within-a-jump-model-to-define-a-derivative-based-constraint/23085)

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**Author:** [@jacob-roth](https://discourse.julialang.org/u/jacob-roth)\
**Replies:** 0\
**Last updated:** [April 12, 2019, 4:27pm UTC](https://discourse.julialang.org/t/jump-use-ad-within-a-jump-model-to-define-a-derivative-based-constraint/23085 "2019-04-12T16:27:14Z")

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I have a JuMP (v0.18.5) model with nonlinear constraints, and I’m trying to encode a new constraint which depends on the Jacobian of the nonlinear constraints. As an example, consider the simpler case of solving a linea…

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## [Treating Variable as Constant in ForwardDiff](https://discourse.julialang.org/t/treating-variable-as-constant-in-forwarddiff/23080)

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**Author:** [@mboutros](https://discourse.julialang.org/u/mboutros)\
**Replies:** 2\
**Last updated:** [April 12, 2019, 3:30pm UTC](https://discourse.julialang.org/t/treating-variable-as-constant-in-forwarddiff/23080 "2019-04-12T15:30:49Z")

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I’ve distilled my use case into a simple example. Essentially, I have an outer function that takes an input and generates a scalar from an inner function. I want ForwardDiff to treat this scalar as a constant when taking…

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## [Optim.jl - No default objective type for IPNewton](https://discourse.julialang.org/t/optim-jl-no-default-objective-type-for-ipnewton/23036)

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**Author:** [@ferrolho](https://discourse.julialang.org/u/ferrolho)\
**Replies:** 5\
**Last updated:** [April 12, 2019, 10:19am UTC](https://discourse.julialang.org/t/optim-jl-no-default-objective-type-for-ipnewton/23036 "2019-04-12T10:19:46Z")

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Please consider the following code snippet using Optim.jl: using Optim dof = 7 fun(x) = 0.0; x0 = fill(0.1, dof) df = TwiceDifferentiable(fun, x0) lx = fill(-1.2, dof); ux = fill(+1.2, dof) dfc = TwiceDifferentiableC…

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## [SDP trace minimization with affine constraints: help to formulate the problem](https://discourse.julialang.org/t/sdp-trace-minimization-with-affine-constraints-help-to-formulate-the-problem/22505)

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**Author:** [@dapz](https://discourse.julialang.org/u/dapz)\
**Replies:** 7\
**Last updated:** [April 10, 2019, 8:35am UTC](https://discourse.julialang.org/t/sdp-trace-minimization-with-affine-constraints-help-to-formulate-the-problem/22505 "2019-04-10T08:35:12Z")

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Hi, I need to solve the following convex optimization problem: min\_{X}\\quad tr(X) s.t. A(X)=b and X semi-definite positive, where A computes rank-1 projections: A(X)=\[\<aᵢaᵢᵀ,X\>\]\_{i=1}^n. However I never really used op…

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## [Running a function with multiple threads inside @btime never ends](https://discourse.julialang.org/t/running-a-function-with-multiple-threads-inside-btime-never-ends/23047)

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**Author:** [@xor0110](https://discourse.julialang.org/u/xor0110)\
**Replies:** 1\
**Last updated:** [April 11, 2019, 6:25pm UTC](https://discourse.julialang.org/t/running-a-function-with-multiple-threads-inside-btime-never-ends/23047 "2019-04-11T18:25:52Z")

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I am trying to debug an SDL application using the experimental multi-threading. It appears to conflict with a parallel for I wrote. I separated this parallel for part just to test it and benchmark separately, and I am ha…

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## [Naive Bayes text classification: what package in Julia?](https://discourse.julialang.org/t/naive-bayes-text-classification-what-package-in-julia/23042)

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**Author:** [@axelle](https://discourse.julialang.org/u/axelle)\
**Replies:** 1\
**Last updated:** [April 11, 2019, 5:33pm UTC](https://discourse.julialang.org/t/naive-bayes-text-classification-what-package-in-julia/23042 "2019-04-11T17:33:57Z")

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Good afternoon, I would like to use Julia for naive Bayes text classification. I have many investment fund names that i would like to regroup under the same master parent which can generally be recognized by looking at …

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## [RigidBodyDynamics : velocity\_range](https://discourse.julialang.org/t/rigidbodydynamics-velocity-range/23004)

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**Author:** [@RogerP](https://discourse.julialang.org/u/RogerP)\
**Replies:** 2\
**Last updated:** [April 11, 2019, 7:28am UTC](https://discourse.julialang.org/t/rigidbodydynamics-velocity-range/23004 "2019-04-11T07:28:46Z")

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I am trying to understand the relationship between v and q̇ using the functions that provide the Jacobians relating the two and I wonder if someone could explain the meaning of the required velocity ranges? The docs say…

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## [Quadratic Programming Problem - CPL](https://discourse.julialang.org/t/quadratic-programming-problem-cpl/21068)

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**Author:** [@Rajat\_Sanyal](https://discourse.julialang.org/u/Rajat_Sanyal)\
**Replies:** 9\
**Last updated:** [April 10, 2019, 4:39pm UTC](https://discourse.julialang.org/t/quadratic-programming-problem-cpl/21068 "2019-04-10T16:39:30Z")

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I am trying to solve a convex QP. Let us consider the following example: using JuMP, CPLEX m = Model(with\_optimizer(CPLEX.Optimizer)) @variable(m,x\[1:5\],lower\_bound=0) A = rand(5,5).\*2 .- 1 c = rand(5,1) A = A'\*A @objec…

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## [Help changing the visualization of my figures](https://discourse.julialang.org/t/help-changing-the-visualization-of-my-figures/22994)

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**Author:** [@muriloasouza](https://discourse.julialang.org/u/muriloasouza)\
**Replies:** 2\
**Last updated:** [April 10, 2019, 3:33pm UTC](https://discourse.julialang.org/t/help-changing-the-visualization-of-my-figures/22994 "2019-04-10T15:33:29Z")

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Hello, i’m ploting these two figures: Using this code: using StatPlots Nt = 33; DHTvI = \[0.948922; 1.84699; 2.33009; 2.82551; 3.35778; 4.14989; 4.70336; 5.57; 6.16913; 6.5514; 6.5514; 2.27957; 2.88751; 3.20105; 3.…

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## [ForwardDiff for functions of several (vector) variables?](https://discourse.julialang.org/t/forwarddiff-for-functions-of-several-vector-variables/22918)

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**Author:** [@zdenek\_hurak](https://discourse.julialang.org/u/zdenek_hurak)\
**Replies:** 2\
**Last updated:** [April 10, 2019, 1:42pm UTC](https://discourse.julialang.org/t/forwarddiff-for-functions-of-several-vector-variables/22918 "2019-04-10T13:42:17Z")

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Is it possible to use ForwardDiff for functions of several variables? In particular, consider a scalar function L(x,u) of two vector variables x and u. I want to compute the gradient of L() with respect to x. From the d…

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